1988 45hp 4cyl runs hot, help

[itspaidfor]

After about 10 minutes of running the motor seems to me to get too hot .no high temp buzzer goes off but the tell tale stream gets some steam off it like hot water in a pot at boil.the water pump impeller ,base ,gaskets have all just been replace even did the garden hose to water tube trick with no aparant blockage .so water flow dosent seem to be the problem.all spark plugs look the same color.have had this problem for a while even before the pump change .motor runs good otherwise .no their is no thermostate on this motor.any ideas ? thanks

 

[WillyBWright]

Re: 1988 45hp 4cyl runs hot, help

It's not unusual, especially if the motor is worked hard. The telltale will be hot, especially after running hard. You should be able to keep your hand in it for a few seconds before it becomes distressingly hot.

However one thing that comes to mind is the rubber exhaust seal just behind the pump. If that's bad, exhaust can enter the water pump. That can throw bubbles into the cooling system and what looks like steam could be the exhaust bubbles releasing their contents.

 

[Remer]

Re: 1988 45hp 4cyl runs hot, help

After about 10 minutes of running the motor seems to me to get too hot .no high temp buzzer goes off but the tell tale stream gets some steam off it like hot water in a pot at boil.the water pump impeller ,base ,gaskets have all just been replace even did the garden hose to water tube trick with no aparant blockage .so water flow dosent seem to be the problem.all spark plugs look the same color.have had this problem for a while even before the pump change .motor runs good otherwise .no their is no thermostate on this motor.any ideas ? thanks

 

[Remer]

Re: 1988 45hp 4cyl runs hot, help

I'm having the same problem witha 1987 Mercury 45 hp 4 cyl. When the motor is started it takes 30 seconds before the water starts passing through the telltale, the flow isn't very strong and does not increase when the throttle is increased. I did not find any blockage in the lower unit tube or the telltale. Have installed a new impeller, have cupped the blades both counter clock wise and clock wise (seems clock wise is the correct direcion). I have run a wire up the lu tube which will go into to the motor chamber and did not pull out any trash. Not looking forward to pulling the power head. Any suggestions?

 

[emckelvy]

Re: 1988 45hp 4cyl runs hot, help

Well, I guess something just one step less extreme than pulling the powerhead to check for obstructions, would be to remove the cylinder block water jacket cover (the one over the end of the block, where the spark plugs stick thru).

It's held on with 1/4" bolts so go easy on them if you've run in salt water. Heat up the area around each bolt with a propane or MAPP gas torch and they'll probably come loose for ya. A little PB Blaster helps too.

Once you get the back cover off, it you see a lot of silt/sediment buildup that's your problem.

Once you get it all cleaned out, pull the lower unit and run water up the copper water tube, it should flush out of the block.

If you don't get a strong flow you've got other internal cooling passages blocked and will probably need to pull the powerhead to check the upper grommet on the water tube, and the exhaust manifold if you don't find any problems with the grommet.

HTH..........ed

 

[Remer]

Re: 1988 45hp 4cyl runs hot, help

Well, I guess something just one step less extreme than pulling the powerhead to check for obstructions, would be to remove the cylinder block water jacket cover (the one over the end of the block, where the spark plugs stick thru).

It's held on with 1/4" bolts so go easy on them if you've run in salt water. Heat up the area around each bolt with a propane or MAPP gas torch and they'll probably come loose for ya. A little PB Blaster helps too.

Once you get the back cover off, it you see a lot of silt/sediment buildup that's your problem.

Once you get it all cleaned out, pull the lower unit and run water up the copper water tube, it should flush out of the block.

If you don't get a strong flow you've got other internal cooling passages blocked and will probably need to pull the powerhead to check the upper grommet on the water tube, and the exhaust manifold if you don't find any problems with the grommet.

HTH..........ed